Preparation of thia-amines



United States Patent 2,754,328 PREPARATION 0F THIA-AMINES Wayne A. Proell, Chicago, 111., assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application June 11, 1953, Serial No. 361,079 15 Claims. (Cl. 260-583) This invention relates to the preparation of thia-amines. More particularly the invention relates to the preparation of secondary thia-alkylamines and tertiary thia-alkylamines.

An object of the invention is the preparation of thiaarnines by a reaction involving an ammonium salt, formaldehyde and a defined thiol. Another object of the invention is a process for the preparation of secondary thiaamines. Still another object is the preparation of tertiary thia-amines. A particular object of the invention is a relatively inexpensive process for the preparation of either secondary thia-alkylamines or tertiary thia-alkylamines by the reaction of formaldehyde, an ammonium salt and either a primary mercaptan or a secondary mercaptan.

It has been found that either secondary thia-amines or tertiary thia-amines or mixtures thereof can be obtained in high yield by the reaction of formaldehyde, a thiol selected from the class consisting of primary mercaptans, secondary mercaptans and aromatic mercaptans wherein a substantial excess over the theoretical reaction quantity of aldehyde and ammonium salt is present; the reaction takes place at a temperature below about 50 C. in an aqueous medium which is maintained at a pH that is numerically lower than about 6. The conditions under which the reaction is carried out determine whether the thin-amine is produced as the thia-amine per se or as the acid salt of the thin-amine.

The thia-amine product is essentially the secondary derivative when the pH of the aqueous medium is maintained numerically lower than about 2. When the pH of the aqueous medium is maintained between about 3 and 5 the thia-amine product is essentially the tertiary derivative.

The process of this invention utilizes formaldehyde and the polymeric forms thereof, such as, paraformaldehyde. The aldehyde may be used per se or in the form of an aqueous solution. 7

The thiols of this invention include all the hydrocarbon thiols except the tertiary thiols, i. e., those wherein the carbon atom immediately adjacent to the sulfur is attached to three other carbon atoms. Thus the operative thiols are selected from the class consisting of primary mercaptans, secondary mercaptans and aromatic mercaptans. The term aromatic mercaptans is equivalent to the terms thiophenols and arylmercaptans. These aromatic mercaptans are intended to include those thiols wherein the sulfur atom is directly joined to a ring carbon atom of a benzene ring or condensed benzene ring. Examples of these aromatic mercaptans are thiophenol, thiocresol, thionaphthol and thioantrachol. The primary mercaptans are intended to include aliphatic mercaptans and substituted aromatic mercaptans and substituted cyclo-aliphatic mercaptans wherein the sulfur atom is attached to a carbon atom present in the substituent group. The secondary mercaptans are intended to include aliphatic mercaptans and cycloaliphatic mercaptans wherein the sulfur atom is directly adjacent to a ring carbon atom.

The preferred thiols are the primary and secondary aliphatic mercaptans which contain not more than 12 carbon atoms. Examples of these preferred primary and secondary aliphatic mercaptans are methyl mercaptan,

captan and secondary butyl mercaptan.

cg 2,754,323 Patented July 10, 1953 The ammonium salts used in the process of this invention may be either the organic or inorganic salts. Examples of suitable ammonium salts are ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium acid sulfate, ammonium acetate, ammonium butyrate, ammonium oxalate, ammonium acid phosphate and ammonium sulfite. The particular salt used in the process will be determined by the desired thia-amine product, i. e., secondary, tertiary or a mixture thereof and the form in which the product is desired; it is possible to obtain the tertiary thia-amine either as the thia-amine per se or as the corresponding thia-amine salt.

When the secondary thia-amine is the desired thiaamine product, the ammonium salts of strong acids are used in order to maintain the aqueous medium at the desired pH of less than about 2. Of course any ammonium salt can be used when the aqueous medium is bufiered at a pH of less than about 2.

When a tertiary thia-alkylamine is the desired thiaamine product, it is preferred to use ammonium salts whose dissociation constant naturally produces a pH between about 3 and 5. However, any ammonium salt which can be bulfered to maintain a pH of about 3 and 5 is suitable for use in this reaction.

Temperature has a very important bearing on the course of the reaction. A reaction temperature above about 50 C. seriously alfects the yield of the desired thia-amine and may entirely prevent the formation of thia-amine. Temperatures above about 50 C. appear to result in the formation of mercaptals. In general about 40 'C. is the preferred upper limit of temperature. Temperatures below about 0 C. may be utilized. However, these low temperatures seriously retard the reaction rate and require extremely prolonged times to produce good yields of the desired thia-amine. It is preferred to operate at a temperature between about 15 and 40 C.

In the formation of a secondary thia-amine by the process of this invention the reaction appears to be:

Thus the theoretical reaction quantities required are equal molar amounts of thiol and aldehyde and 0.5 mol of ammonium ion. The formation of the tertiary thia-amine appears to follow the following reaction:

In this reaction theoretically one-third mol of ammonium ion is required per mol of thiol. However, it has been found in both reactions that when about the theoretical reaction quantities of thiol and aldehyde are used, the reaction does not yield the desired thia-amine and appears to yield hemimercaptals. In order to obtain thiaamine as the reaction product, it is necessary to use an amount of aldehyde and ammonium salt in excess of the theoretical reaction quantity. It is preferred to operate with a mol ratio of aldehyde to thiol of between about 2:1 and 4:1. It is preferred to operate with an equivalent mol ratio of ammonium ion to thiol of between about 1:1 and 2:1.

The reaction is carried out in an aqueous medium which may be ordinary water or an aqueous solution of a buffering compound. The pH of the aqueous medium must be maintained numerically below about 6 in order to obtain thia-amine as the product. Furthermore, in order to obtain tertiary thia-amine as the essentially only thia-amine product, it is necessary to maintain the pH of the aqueous medium between about 3 and 5. In order to obtain secondary thia-amine as the essentially only thia-amineprod uct, it is necessary to maintain the pH of the aqueous medium below about 2 and preferably between about 1 and 2. Very low pHs have an adverse effect on the yield of thia-amine.

As the reaction takes place in an aqueous medium, the reactants must be appreciably soluble in the aqueous medium under reaction conditions of temperature. It is preferred to operate under conditions of pressure such that dilute hydrochloric acid. The oil was found to contain 38.0 weight percent of sulfur and 7.84 weight percent of nitrogen. Di(thiabutyl)amine contains 38.8% sulfur and 8.48% nitrogen.

low boiling reactants will be maintained in the liquid state 5 Test 2 illustrates the effect of elevated temperatures on at reaction temperature. the course of the reaction. In this test where the tempera- In order to illustrate the results obtainable with the ture reached 70 C. no thia-amine was obtained and the process of this invention, the results of reactions carried reaction product appeared to be a mercaptal. V out at difierent conditions are set out below. Table I Test 6 shows the eflect of very low p i-Ion the product contains the results of reactions intended to produce secyield. In this test wherein the pH was lowered by the adondary thia-alkylamines "as the reaction product. Table dition of 2 mols of hydrochloric acid, only of the II contains the results of reactions intended to produce desired thia-amine hydrochloride was obtained. tertiary thia-alkylamines as the reaction product. TEST 11 These reactions were carried out using a glass flask pro- V vrded with amotordrrven stirrerandheatmg means. The 15 This test illustrates a typical preparation of a tertiary aldehyde mall the tests was an aqueous solution of forum thia a1ky1amine In this test 154 g (2 mols) of ammo; i h g (abmitw weight percent). The aqueous i nium acetate was dissolved in 400 g. of aqueous 37% a h d thepartlculaf ammomum i p awded formaldehyde ('5 mols) and 1 mol of n-butyl mercaptan to the fl k and Stirred l had dlssolved' P was added slowly thereto. The pH of the mixture slowly l the iwP e m of l l decreasad marked) decreased from 4.5 to 4.0 and the temperature rose to a dunng thls sohmon- The meniaPtan was added SIQWIY maximum of 32 C. After a 30-minute reaction time a to h a Usually a V sharp use m temPe-ramre visc'ous white oil was recovered from the flask. This oil s notedh temperature 0f tbs Contents 9 the flask was distilled at 0.1 mm. of Hg. The fraction boiling at normally dropped q i after completfon 9 the 115, C. contained 29.2% sulfur and 4.32% nitrogen. fip d h ammomun? chl9nde or Tri(thiahexyl)amine contains 29.7% sulfur and 4.33% momum oxalate was the salt and a thia-amme was pronitrogen du'ced, white crystals precipitated from the liquid shortly TEST 15 after the first addition of mercaptan. In these runs the v V V J crystals were recovered by filtration. The free thia-amine amp 9 U P YU W Charged was recovered, by contacting the crystals with a dilute distillation fiaskand distilled at a pot temperatore of bequ''du' a ti 1 i tween and 100 C. Thermal decomposition of the TEST 8 thia-amine was inhlbited to some extent by the presence I of a slight amount of sodium hydroxide in the flask. The This test is typical of the preparation of a secondary temperature in the flask rose very rapidly until when about thia-alkylamine. In this test 212 g. (4 mols) of am- 50% of the material was distilled the temperature was monium chloride was dissolved in 800 g. of aqueous 37% about 340 C. (corrected to 760 mm; Hg). The material formaldehyde (10 mols) and 400 g. (6.4 mols) of ethyl in the flask 'was a heavy oil which reacted readily with mercaptan were slowly added. The maximum temperadilute hydrochloric acid to give white crystals. The cure was 32C. The pasty suspension of crystals was overhead from this distillation operation contained a filtered, the recovered crystals were contacted with an 40 considerable amount of mercaptan. Apparently the secexcess of dilute aqueous sodium hydroxide. An oil was ondary thia-amines readily condense upon heating to form obtained. The oil-water mixture was extracted with ether polytbia-amines and mercaptan. The polythia-amines and 470 g. of oil were recovered from the ether. The have chemical reactivity quite similar to the secondary oil was water-white in color, had a very bad odor and t bia-amine, thereby indicating the presence of secondary formed crystalline salts immediately when admixed with linkages. It has been found that secondary thia-alkyl- TABLE I Secondary thia-alkyla'mines riskier 1*11101 Amine" Testy dehyde, NHACI, Time, Temp. Yield, 7 Product No. Mols Mols Hrs. C. Wt.

Mols Type Percent V 4 2 1 n-Butyl 2 15-49 100' (ot'rras'ornnNn-nol. .4- 2 1 .do.. 2 20-70 0 (G4HlS):UH:-

1 2.2 1 no 1 22 0 on. v 4 2 0. 5 0. 5 20 100 (Gc'HaS CH2)2NH-HO1. 5 2 1 15 "reassure-aa- 1 5 iroinisnoiaimm). 5 2 1.4 Ethyl, 1 8 21 54 (OH5SOHQ),HNHOL l0 4 6.4 o '1 32 '95 .(C:H nS QH2):HN'HQl. 5 2 .1 tButyl 0.3 30 0 Gontain'ed'no nitrogen. 4 2 0.5 n-Dodecyl 1 1032 100 Amine hydrochloride.

pH lowered by presence 01 2 mols of HCl.

.. been. .Tm r thiq-q lwl z iw a. V Ammonium Thiol -A1:1.1inri" Formal- Salt Time, 'Temp., Yield, Test No. dehyde, Hrs. C. .;..Wt. Product ols H Percent 9 T R M015 TY??? 5 2 Acetate. '1 n B utyLH 0:6 32 '(CAHiSCH hN 1.2 2 do 1 o; 1:1 2.6 50' (O; tSOHz):

T111o1 50%). 4 1 5 do 1.4 Ethyl '1 25 92 (C:H5SCHz)3N. 5 1 Oxalate. 1 11:13am.-- 10 as (QiH'0SCH2)5N-Hg0a0d amines containing from about 2 to 24 carbon atoms in each alkyl group readily condense to polythia-alkylamines when heated to about incipient decomposition temperature. The degree of condensation appears to be dependent upon the length of time at which the material is maintained at the elevated temperature.

TEST 16 Tri(2-thiahexyl)amine was heated in a distillation fiask. The thia-amine distilled smoothly at about 115 C. at 0.1 mm. Hg without any evidence of decomposition or condensation reaction. Thus unlike the secondary thiaamines the tertiary thia-amines are quite stable under exposure to elevated temperatures.

TEST 17 In this test 2 mols of ammonium chloride were dissolved in 38% aqueous formaldehyde mols) and 1.3 rnols of hydrogen sulfide were introduced slowly into the aqueous solution. The temperature in the flask rose rapidly to 70 C. and dropped slowly after the cessation of H28 addition to about C. during the reaction time of 1 hour. Nothing precipitated from the aqueous medium. The aqueous medium was neutralized by the addition of dilute sodium hydroxide solution. Some material separated out of the aqueous medium and was recovered. This material represented about a 100% yield based on formaldehyde, ammonium ion and H charged. Analysis of this material indicated it to be a reaction product wherein the hydrogen sulfide had reacted in a manner similar to a thiol.

The amine is a gummy, semi-aliphatic solid which possesses excellent adhesive properties toward glass, metal and organic films. Another notable characteristic of this amine is its extremely low solubility in common organic solvents such as naphtha, alcohol, ether and acetone.

Most surprisingly is the extreme high solubility of the amine-acid salt, e. g., amine hydrochloride in water. This characteristic is in complete contrast with the extremely low solubility of the thia-amine-salts as had been described earlier.

TEST 18 In this test 4 mols of ammonium chloride were dissolved in water and 10 mols of crotonaldehyde were added thereto. Ethyl mercaptan to the amount of 6 mols was slowly added. The temperature of the mixture remained at about 22 C. during minutes of stirring. No crystals were pro-duced and apparently no reaction took place.

TEST 19 In this test 4 mols of ammonium chloride were dissolved in water and 10 mols of acetaldehyde added thereto. Ethyl mercaptan to the amount of 6 mols was slowly added. The temperature of the mixture rose from 22 C. to 30 C. during 30 minutes of stirring but no crystals were produced.

For purposes of illustration a preferred method of making the secondary thia-alkylamines is described. A jacketed kettle provided with a mechanical stirrer is a preferred reaction vessel. Aqueous formaldehyde and ammonium chloride are added to the vessel and stirred until the ammonium chloride is dissolved. A mercaptan, e. g., ethyl mercaptan, is then added slowly to the reactor. Cooling water is circulated in the jacket of the vessel to maintain the temperature therein at about 30 .C. The contents of the reactor are stirred for about 30 minutes after the mercaptan addition is complete. The slurry of crystalline thia-amine hydrochloride may be withdrawn from the reactor and the crystals recovered by filtration. When the thia-arnine is the desired prodnot, it is preferred to decompose the acid salt with dilute aqueous sodium hydroxide in a separate operation. The thia-amine is readily recovered by decantation from the aqueous phase. The mother liquor from the acid salt recovery is recycled to the reaction vessel. Suflicient paraformaldehyde is introduced to provide the necessary excess of formaldehyde without causing dilution of the aqueous solution. Sufficient ammonium chloride is introduced into the reaction vessel to provide the necessary excess of this salt. Then the mercaptan is introduced into the aqueous medium and the cycle begun.

A preferred method of operation for the preparation of tertiary thia-alkylamine is described. The reaction vessel of the preceding paragraph is preferred. The first batch is prepared by charging aqueous formaldehyde and ammonium acetate to the reactor and then the mercaptan is added slowly to the reaction vessel. At the pH provided by the acetate salt the thia-alkylamine is formed and separates as an oil layer. The lower aqueous layer is withdrawn separately and the upper amine layer is withdrawn separately. The aqueous layer is recycled to the reaction vessel; makeup formaldehyde in the form of paraformaldehyde is charged to avoid dilution. This particular reaction results in the formation of acetic acid as a byproduct. Therefore, ammonia is charged to the reaction vessel and the ammonium acetate formed therein by reaction with the acetic acid. The mercaptan is then charged to the reaction vessel and the cycle begun.

The thia-amines are useful as lubricating oil additives and as rubber accelerators. Probably a more important use of these materials is as intermediates in the preparation of detergents, e. g., a thia-alkylamine containing from 10 to 18 carbon atoms can be reacted with ethylene oxide to form a non-ionic detergent.

The thia-alkylamine acid salts are essentially insoluble in water. Surprisingly the surface of the crystal formed by these salts sheds water almost completely, i. e., possesses extremely low wettability. These salts can be used to impregnate fabrics and porous materials in order to impart water repellency thereto.

Thus having described the invention, what is claimed is:

1. A process comprising reacting formaldehyde, a thiol selected from the class consisting of primary alkyl mercaptans and secondary alkyl mercaptans and an ammonium salt containing not more than 12 carbon atoms, wherein the amount of aldehyde and salt is in substantial excess of the theoretical reaction quantity, at a temperature of between about 0 and 50 C., in an aqueous medium maintained at a pH numerically lower than about 6, and separating a reaction product containing a thia-amine selected from at least one member of the class consisting of secondary thia-amines and tertiary thia-amines from aqueous medium.

2. The process of claim 1 wherein the reaction is continued for a time suflicient to substantially complete the reaction to the thia-amine containing product.

3. The process of claim 1 wherein the mol ratio of aldehyde to thiol is between about 2:1 and 4:1.

4. The process of claim 1 wherein said temperature is between about 15 and 40 C.

5. The process of claim 1 wherein said aldehyde is paraformaldehyde.

6. The process of claim 1 wherein said thiol is an aliphatic mercaptan containing from 1 to 4 carbon atoms.

7. A process for preparing a secondary thia-amine, which process comprises reacting formaldehyde, a thiol selected from the class consisting of primary alkyl mercaptans and secondary alkyl mercaptans containing not more than 12 carbon atoms and an ammonium salt of a strong acid, wherein the amount of aldehyde and salt is in substantail excess of the theoretical reaction quantity, at a temperature between about 0 and 50 C., in an aqueous medium maintained at a pH numerically lower than about 2 and separating secondary thia-amine containing reaction product from aqueous medium.

8. The process of claim 7 wherein said temperature is between about 15 C. and 40 C.

9. The process of claim 7 wherein the mol ratio of aldehyde:thio1:salt is between about 2:-1 :-1 and 4:1:2.

10. The process of claim 7 wherein said salt is ammonium chloride.

11. A process for preparing a tertiary thia-amine, which process comprises reacting formaldehyde, a thiol selected from the class consisting of primary aikyl mercaptans and secondary alkyl mercaptans containing not more than 12 carbon atoms and an ammonium salt of a strong acid, wherein the amount of aldehyde and salt is in substantial excess of the theoretical reaction quantity, at a temperature between about 0 and 50 C., in an aqueous medium maintained at a pH between about 3 and 5.

12. The process of claim 11 wherein a tertiary thiaamine is recovered from the reaction mixture.

13. The process of claim 11 wherein said temperature is between about 15 C. and '40" C.

References Cited in the file 'of this patent UNITED STATES PATENTS Jones Oct. 24, 1939 Mathe's' Nov. 28, 1944 OTHER REFERENCES Dbilgh'erty at al.: roar. Chem. Soc? 1933 vol; 55,'pp. 4588-93. 

1. A PROCESS COMPRISING REACTING FORMALDEHYDE, A THIOL SELECTED FROM THE CLASS CONSISTING OF PRIMARY ALKYL MERCAPTANS AND SECONDARY ALKYL MERCAPTANS AND AN AMMONIUM SALT CONTAINING NOT MORE THAN 12 CARBON ATOMS, WHEREIN THE AMOUNT OF ALDEHYDE AND SALT IS IN SUBSTANTIAL EXCESS OF THE THEORETICAL REACTION QUANTITY, AT A TEMPERATURE OF BETWEEN ABOUT 0* AND 50* C., IN AN AQUEOUS MEDIUM MAINTAINED AT A PH NUMERICALLY LOWER THAN ABOUT 6, AND SEPARATING A REACTION PRODICT CONTAINING A THIA-AMINE SELECTED FROM AT LEAST ONE MEMBER OF THE CLASS CONSISTING OF SECONDARY THIA-AMINES AND TERTIARY THIA-AMINES FROM AQUEOUS MEDIUM. 